| atrium cordis | (n) the upper chamber of each half of the heart, Syn. atrium of the heart |
| left atrium | (n) the left upper chamber of the heart that receives blood from the pulmonary veins, Syn. left atrium of the heart, atrium sinistrum |
| right atrium | (n) the right upper chamber of the heart that receives blood from the venae cavae and coronary sinus, Syn. right atrium of the heart, atrium dextrum |